EditText中输入的内容不能小于一位数字切不能以0开头

 num.addTextChangedListener(new TextWatcher() {            @Override            public void onTextChanged(CharSequence s, int start, int before, int count) {                if (num.toString().equals("0") || s.toString().startsWith("0")                    || num.toString().equals("") || s.toString().trim().length() == 0) {                    num.setText("1");                }            }            @Override            public void beforeTextChanged(CharSequence s, int start, int count, int after) {            }            @Override            public void afterTextChanged(Editable s) {                if (fbId == 0) {                    sendToast();                } else {                    getManureFromService(WheelMain.N_num, WheelMain.P_num, WheelMain.K_num);                }            }        });